The present invention is related to a rolling bearing for the purpose of supporting a shaft rotating at a high speed, such as the main shaft of machine tools, and specifically to a lubrication system used for the rolling bearing to lubricate the rolling bearing.
The main shaft of machine tools rotates at a high speed during use. Accordingly, the main shaft like this needs to be rotatably supported by a rolling bearing and, during rotating, be supplied with an enough amount of lubrication oil into the rolling bearing. A device for the purpose of supplying the lubrication oil to a rolling bearing which is used to rotatably support the main shaft inside the housing, Japanese Patent Publication No. Toku Kai Hei 10-299784 discloses a lubrication system for a rolling bearing, which has a structure as shown in FIG. 5. The rolling bearing 1 in this Publication is provided with an inner ring 4 which has an inner ring raceway 5 on its outer peripheral sutrface and is fitted on and fixed by the main shaft (not shown) rotating at a high speed during use. And, the rolling bearing 1 is provided with an outer ring 6 which has an outer ring raceway 7 on its inner peripheral surface and is fitted into and fixed by the housing (not shown). And, a plurality of rolling elements 8 are rotatably supported by a retainer 9 between the inner ring raceway 5 and the outer ring raceway 7.
And, adjacent to the inner ring 4 around the main shaft, first and the second inner ring spacers 10, 11 are provided sequentially from the side of the inner ring 4. On the other hand, inside the housing, adjacent to the outer ring 6, an outer ring spacer 2 is provided. The lubrication system for the rolling bearing is constructed to freely supply the lubrication oil through a lubrication oil path 3 provided in the outer ring spacer 2.
Specifically, the lubrication oil path 3 is provided inside the outer ring spacer 2, and the lubrication oil (oil air or oil mist) supplied into the lubrication oil path 3 is freely supplied into the space 15 between the outer peripheral surface of the inner ring 4 and the inner peripheral surface of the outer ring 6, where the plurality of rolling elements 8 are provided. That is to say, a nozzle hole 13 is provided at the outer ring spacer 2, and the lubrication oil supplied into the lubrication oil path 3 is spouted from the nozzle hole 13. There is an oil supplying gap 14 provided between the inner peripheral surface of the outer ring spacer 2 and the outer peripheral surface of the inner ring spacer 10, and the lubrication oil spouted from the nozzle hole 13 is disgorged from the end opening of the oil supplying gap 14 into the space 15 within the rolling bearing I where the rolling elements 8 are provided. The end opening of the oil supplying gap 14 exists on the radially inner side of the axially medium portion of the inner peripheral surface of the outer ring 6 in the rolling bearing 1. Accordingly, when rotating at a high speed, the lubrication oil, without being affected by the air curtain formed at both end openings of the space 15, is efficiently attached to the rolling surface of each of the rolling elements 8.
In the case of the conventional lubrication system of the rolling bearing constructed and acting as mentioned above, the lubrication of the rolling bearing 1 is good, but it is hard to highly increase the rotating speed of the main shaft. The reason of this problem is mentioned next. For the purpose of highly increasing the rotating speed of the main shaft supported by the rolling bearing 1, the pitch circle diameter (PCD) of the rolling bearing 1 needs to be small.
On the other hand, in the case of the conventional structure as shown in FIG. 5, a part of the outer ring spacer 2 is positioned on the radially inner side of the outer ring 6 and the retainer 9, and then the respective inner diameter of the outer ring 6 and the retainer 9 is not able to be reduced and the PCD is not be ablc to be reduced. Accordingly, as mentioned above, it is difficult to highly increase the speed of the main shaft. And, because of the structure wherein the outer ring spacer 2 is projected into the radially inner side of the retainer 9, the operation of manufacturing the outer ring spacer 2 is troublesome to cause its cost.
Another lubrication system of the rolling bearing for rotatably supporting the main shaft of the machine tools is disclosed, for examples, in Japanese Patent Publication No. Toku Kai Hei 06-264934 and No. Toku Kai Hei 10-231843, but has the similar problems.
Further, the lubrication system of the rolling bearing disclosed in Japanese Patent Publication No. Toku Kai Hei 06-235425, as shown in FIG. 6, is constructed to have a hollow first inner ring spacer 23 between the inner ring 4 and the second inner ring spacer 11 such that part of the hollow inner ring spacer 23 is positioned on the radially inner side of the retainer 9 and the lubrication oil supplied from the outer ring spacer 2b into the inner ring spacer 23 is disgorged from a nozzle hole 13a provided in the inner ring spacer 23 to the rolling surface of rolling elements 8. In the case of this conventional system, because the inner ring spacer 23 used has a larger outer diameter than the inner ring raceway 5, not only PCD is hard to be sufficiently decreased, but also the structure material complexity and the cost increase can not be avoided.
The present invention is developed for realizing a lubrication system for the rolling bearing, solving all of the above problems.
An object of the present invention is to provide a lubrication system for the rolling bearing having a guide slope surface tilted with respect to the rotation axis and having no portion such as step, oil ditch, edge where the sloping direction and/or sloping angle suddenly change.